1. Field of the Invention
This invention relates to catalytic reaction apparatus such as for producing product gases from a feedstock.
2. Description of the Prior Art
Catalytic reaction apparatus for converting hydrocarbon fuels to useful industrial gases, such as hydrogen, are well known in the art. They are generally designed for high product gas yield. Equipment size has been generally of secondary importance since the cost to produce the product gas is a small fraction of the price of the products made from the product gas. The most common process for producing hydrogen is steam reforming a hydrocarbon fuel by passing it through heated catalyst filled reaction tubes disposed within a furnace. Typically the reaction tubes are 20-40 feet long and the primary mode (on the order of 70%) of heat transfer is by radiation from the furnace walls to the reaction tubes. This requires relatively large spacing between the tubes and placement of the tubes adjacent the walls of the furnace in order that each tube is uniformly heated by radiation from the walls. These commercial hydrogen generation plants have a very high rate of heat transfer, on the order of 20,000-25,000 Btu/hr per ft.sup.2 of reaction tube surface area; however, because this type of system is primarily dependent upon radiant heat, reactor thermal efficiency is only 40-60%. Although high hydrogen conversion rates can be achieved, a large percent of the heat energy produced in the furnace leaves the furnace in the form of high temperature exhaust gases (i.e., waste heat). Thus, in order to have high heating rates large amounts of fuel are burned. If the heat energy is not used in a separate process, such as to produce steam, it would have to be thrown away. Even if the waste heat is used, it is not being used to produce hydrogen, thereby reducing reactor thermal efficiency and increasing the cost of the hydrogen being produced.
Along with the development of the fuel cell power plant came the need for low cost hydrogen as fuel as well as the need for low equipment cost in order for the fuel cell power plant to compete economically with existing electricity generating equipment. These needs brought additional incentive into the marketplace to reduce the size and the operating cost of fuel processing apparatus for the generation of hydrogen from hydrocarbon fuels. Mertens U.S. Pat. No. 3,144,312 and Dantowitz, U.S. Pat. No. 3,541,729, both attempt to reduce the size of reaction apparatus while also increasing thermal efficiency. The extent to which they succeed, if they succeed at all, cannot readily be determined; however, hereinafter in the specification Applicant will point out the shortcomings of these designs as compared to Applicant's invention.
Corrigan U.S. Pat. No. 3,909,299, of common assignee with the present invention, shows a steam reforming reactor design having some desirable features, but it too is not as efficient nor can it be as compact as Applicant's invention hereinafter described.